Auto-injector

Abstract

An auto-injector for administering a dose of a liquid medicament includes an elongate housing arranged to contain a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament, the housing having a distal end and a proximal end with an orifice intended to be applied against an injection site. The syringe is slidably arranged with respect to the housing. A spring capable of, upon activation: pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end (P), operating the syringe to supply the dose of medicament (M), and retracting the syringe with the needle into the covered position. After delivering the medicament, an activator arranged to lock the spring in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring for injection.

The invention claimed is: 
     
         1 . An auto-injector comprising:
 a cylindrical housing defining a longitudinal axis extending from a proximal end of the cylindrical housing to a distal end of the cylindrical housing, the proximal end of the cylindrical housing configured to directly contact an injection site;   a syringe carrier configured to retain a syringe containing a medicament, the auto-injector being configured such that the syringe carrier remains in an initial position relative to the cylindrical housing by an engagement between the syringe carrier and a plunger rod as a needle shield is removed from a proximal end of the syringe;   a sleeve disposed in the cylindrical housing, the syringe carrier being configured to (i) slide within the sleeve during needle insertion, and (ii) be slidably coupled to the sleeve during needle retraction, a distal end of the sleeve defining a distal opening that (i) extends axially through the distal end of the sleeve and (ii) is located concentrically about the longitudinal axis of the cylindrical housing, a surface at the distal end of the sleeve configured to releasably engage a distal portion of the plunger rod to releasably hold the plunger rod in a distal position within the cylindrical housing against a biasing force of a compression drive spring that biases the plunger rod proximally relative to the sleeve, the plunger rod extending through the distal opening and a distal end of the plunger rod being distal to the distal end of the sleeve when the plunger rod is in the distal position,   an axially-extending sidewall of the sleeve defining a longitudinal opening sized to allow a decoupling member to (i) extend through the longitudinal opening and (ii) slide axially relative to the longitudinal opening as the plunger rod moves proximally from the distal position such that a proximal-facing surface of the decoupling member engages a distally-facing surface of a resilient arm to release the resilient arm from being engaged to a first protrusion of the sleeve, the auto-injector being configured such that after the resilient arm has been released from being engaged to the first protrusion the sleeve moves in a distal direction relative to the cylindrical housing to retract a needle of the syringe into the cylindrical housing when the syringe is retained by the syringe carrier,   a proximal-facing surface inside the sleeve engaged to a distal end of the compression drive spring, and a proximal end of the compression drive spring coupled to the plunger rod via an outer protrusion of the plunger rod such that the plunger rod and the decoupling member are biased proximally relative to the sleeve;   a cap configured to be releasably attached to the proximal end of the cylindrical housing to cover the proximal end of the cylindrical housing, the auto-injector being configured such that the syringe carrier engages the plunger rod to limit proximal movement of the syringe carrier relative to the plunger rod when the cap is attached to the proximal end of the cylindrical housing, the cap being configured such that removal of the cap from the proximal end of the cylindrical housing removes the needle shield from the proximal end of the syringe;   a button disposed at the distal end of the cylindrical housing, the button comprising a proximally-extending portion with an inward protrusion configured to slidably engage a distal portion of the sleeve;   a safety member disposed at a distal portion of the cylindrical housing, the safety member configured to (i) limit a proximal movement of the button relative to the cylindrical housing when the safety member is in a first position relative to the cylindrical housing, and (ii) allow the proximal movement of the button relative to the cylindrical housing when the safety member is in a second position relative to the cylindrical housing, the auto-injector being configured such that after a user moves the safety member from the first position to the second position the user can move the button proximally relative to the cylindrical housing; and   a collar attached to the cylindrical housing, the collar containing a viscous substance for delaying the retraction of the needle into the cylindrical housing after the resilient arm has been released from being engaged to the first protrusion,   wherein the cylindrical housing comprises at least one window for viewing the syringe when the syringe is retained by the syringe carrier.   
     
     
         2 . The auto-injector of  claim 1 , wherein the decoupling member and the plunger rod are distinct from each other. 
     
     
         3 . The auto-injector of  claim 1 , wherein the sleeve is a monolithic structure. 
     
     
         4 . The auto-injector of  claim 1 , wherein the auto-injector is configured such that the sleeve does not axially move relative to the cylindrical housing until after the resilient arm has been released from being engaged to the first protrusion. 
     
     
         5 . The auto-injector of  claim 1 , wherein the auto-injector is configured such that the syringe carrier remains in the initial position by the engagement between the syringe carrier and the plunger rod when the cap is attached to the proximal end of the cylindrical housing. 
     
     
         6 . The auto-injector of  claim 1 , wherein the first protrusion is located proximal to a distal end of the longitudinal opening. 
     
     
         7 . The auto-injector of  claim 1 , comprising the syringe containing the medicament. 
     
     
         8 . An auto-injector comprising:
 a cylindrical housing defining a longitudinal axis extending from a proximal end of the cylindrical housing to a distal end of the cylindrical housing, the proximal end of the cylindrical housing configured to directly contact an injection site;   a syringe carrier configured to retain a syringe containing a medicament, the auto-injector being configured such that the syringe carrier remains in an initial position relative to the cylindrical housing by an engagement between the syringe carrier and a plunger rod as a needle shield is removed from a proximal end of the syringe;   a sleeve disposed in the cylindrical housing, the syringe carrier is configured to (i) slide within the sleeve during needle insertion, and (ii) be slidably coupled to the sleeve during needle retraction,   a distal end of the sleeve defining a distal opening that (i) extends axially through the distal end of the sleeve and (ii) is located concentrically about the longitudinal axis of the cylindrical housing, a surface at the distal end of the sleeve configured to releasably engage a distal portion of the plunger rod to releasably hold the plunger rod in a distal position within the cylindrical housing against a biasing force of a compression drive spring that biases the plunger rod proximally relative to the sleeve, the plunger rod extending through the distal opening and a distal end of the plunger rod being distal to the distal end of the sleeve when the plunger rod is in the distal position, p 1  an axially-extending sidewall of the sleeve defining a longitudinal opening sized to allow a decoupling member to (i) extend through the longitudinal opening and (ii) slide axially relative to the longitudinal opening as the plunger rod moves proximally from the distal position such that a proximal-facing surface of the decoupling member engages a distally-facing surface of a resilient arm to release the resilient arm from being engaged to a first protrusion of the sleeve, the auto-injector being configured such that after the resilient arm has been released from being engaged to the first protrusion the sleeve moves in a distal direction relative to the cylindrical housing to retract a needle of the syringe into the cylindrical housing when the syringe is retained by the syringe carrier; and   a collar attached to the cylindrical housing, the collar containing a viscous substance for delaying the retraction of the needle into the cylindrical housing after the resilient arm has been released from being engaged to the first protrusion,   wherein the cylindrical housing comprises at least one viewing window for viewing the syringe when the syringe is retained by the syringe carrier.   
     
     
         9 . The auto-injector of  claim 8 , comprising a cap configured to be releasably attached to the proximal end of the cylindrical housing to cover the proximal end of the cylindrical housing, the auto-injector being configured such that the syringe carrier engages the plunger rod to limit proximal movement of the syringe carrier relative to the plunger rod when the cap is attached to the proximal end of the cylindrical housing. 
     
     
         10 . The auto-injector of  claim 9 , wherein the auto-injector is configured such that the syringe carrier remains in the initial position by the engagement between the syringe carrier and the plunger rod to limit proximal movement of the syringe carrier relative to the plunger rod when the cap is attached to the proximal end of the cylindrical housing. 
     
     
         11 . The auto-injector of  claim 8 , comprising a button disposed at the distal end of the cylindrical housing, the button comprising a proximally-extending portion with an inward protrusion configured to slidably engage a distal portion of the sleeve. 
     
     
         12 . The auto-injector of  claim 11 , comprising a safety member disposed at a distal portion of the cylindrical housing, the safety member configured to (i) limit a proximal movement of the button relative to the cylindrical housing when the safety member is in a first position relative to the cylindrical housing, and (ii) allow the proximal movement of the button relative to the cylindrical housing when the safety member is in a second position relative to the cylindrical housing, the auto-injector being configured such that after a user moves the safety member from the first position to the second position the user can move the button proximally relative to the cylindrical housing. 
     
     
         13 . The auto-injector of  claim 8 , wherein a proximal-facing surface inside the sleeve is engaged to a distal end of the compression drive spring, and a proximal end of the compression drive spring is coupled to the plunger rod via an outer protrusion of the plunger rod such that the plunger rod and the decoupling member are biased proximally relative to the sleeve. 
     
     
         14 . The auto-injector of  claim 8 , wherein the decoupling member and the plunger rod are separable from each other. 
     
     
         15 . The auto-injector of  claim 8 , wherein the sleeve is a monolithic structure. 
     
     
         16 . An auto-injector comprising:
 a cylindrical housing defining a longitudinal axis extending from a proximal end of the cylindrical housing to a distal end of the cylindrical housing, the proximal end of the cylindrical housing configured to directly contact an injection site;   a syringe carrier configured to retain a syringe containing a medicament, the auto-injector being configured such that the syringe carrier remains in an initial position relative to the cylindrical housing by an engagement between the syringe carrier and a plunger rod as a needle shield is removed from a proximal end of the syringe;   a sleeve disposed in the cylindrical housing, the syringe carrier is configured to (i) slide within the sleeve during needle insertion, and (ii) be slidably coupled to the sleeve during needle retraction,   a distal end of the sleeve defining a distal opening that (i) extends axially through the distal end of the sleeve and (ii) is located concentrically about the longitudinal axis of the cylindrical housing, a surface at the distal end of the sleeve configured to releasably engage a distal portion of the plunger rod to releasably hold the plunger rod in a distal position within the cylindrical housing against a biasing force of a compression drive spring that biases the plunger rod proximally relative to the sleeve, the plunger rod extending through the distal opening and a distal end of the plunger rod being distal to the distal end of the sleeve when the plunger rod is in the distal position; and   a collar attached to the cylindrical housing, the collar containing a viscous substance for delaying needle retraction,   wherein the cylindrical housing comprises at least one viewing window for viewing the syringe when the syringe is retained by the syringe carrier.   
     
     
         17 . The auto-injector of  claim 16 , wherein an axially-extending sidewall of the sleeve defines a longitudinal opening that is sized to allow a decoupling member to (i) extend through the longitudinal opening and (ii) slide axially relative to the longitudinal opening as the plunger rod moves proximally from the distal position such that a proximal-facing surface of the decoupling member engages a distally-facing surface of a resilient arm to release the resilient arm from being engaged to a first protrusion of the sleeve. 
     
     
         18 . The auto-injector of  claim 17 , wherein the auto-injector is configured such that after the resilient arm has been released from being engaged to the first protrusion the sleeve moves in a distal direction relative to the cylindrical housing to retract a needle of the syringe into the cylindrical housing when the syringe is retained by the syringe carrier. 
     
     
         19 . The auto-injector of  claim 17 , wherein a proximal-facing surface inside the sleeve is engaged to a distal end of the compression drive spring, and a proximal end of the compression drive spring is coupled to the plunger rod via an outer protrusion of the plunger rod to bias the sleeve axially apart from the plunger rod and the decoupling member. 
     
     
         20 . The auto-injector of  claim 19 , wherein the decoupling member extends outward of the outer protrusion of the plunger rod. 
     
     
         21 . The auto-injector of  claim 19 , wherein the decoupling member and the plunger rod are distinct components of the auto-injector. 
     
     
         22 . The auto-injector of  claim 16 , comprising a cap configured to be releasably attached to the proximal end of the cylindrical housing to cover the proximal end of the cylindrical housing, the auto-injector being configured such that the syringe carrier engages the plunger rod to limit proximal movement of the syringe carrier relative to the plunger rod when the cap is attached to the proximal end of the cylindrical housing. 
     
     
         23 . The auto-injector of  claim 22 , wherein the auto-injector is configured such that the syringe carrier remains in the initial position by the engagement between the syringe carrier and the plunger rod when the cap is attached to the proximal end of the cylindrical housing. 
     
     
         24 . The auto-injector of  claim 16 , comprising a button disposed at the distal end of the cylindrical housing, the button comprising a proximally-extending portion with an inward protrusion configured to slidably engage a distal portion of the sleeve. 
     
     
         25 . The auto-injector of  claim 16 , wherein the sleeve is a monolithic structure. 
     
     
         26 . An auto-injector comprising:
 a housing defining a longitudinal axis extending from a proximal end of the housing to a distal end of the housing, the proximal end of the housing configured to directly contact an injection site;   a syringe carrier configured to retain a syringe containing a medicament, the auto-injector being configured such that the syringe carrier remains in an initial position relative to the housing as a needle shield is removed from a proximal end of the syringe;   a sleeve disposed in the housing, the syringe carrier being configured to (i) slide within the sleeve during needle insertion, and (ii) be slidably coupled to the sleeve during needle retraction; and   a collar attached to the housing, the collar containing a viscous substance for delaying needle retraction,   wherein the housing comprises at least one viewing window for viewing the syringe when the syringe is retained by the syringe carrier.   
     
     
         27 . The auto-injector of  claim 26 , wherein a distal end of the sleeve defines a distal opening that (i) extends axially through the distal end of the sleeve and (ii) is located concentrically about the longitudinal axis of the housing, the sleeve configured to releasably hold a plunger rod of the auto-injector in a distal position within the housing against a biasing force of a compression drive spring. 
     
     
         28 . The auto-injector of  claim 26 , wherein the sleeve is a monolithic structure. 
     
     
         29 . The auto-injector of  claim 26 , comprising a cap configured to be releasably attached to the proximal end of the housing to cover the proximal end of the housing, the cap being configured such that removal of the cap from the proximal end of the housing removes the needle shield from the proximal end of the syringe. 
     
     
         30 . The auto-injector of  claim 26 , comprising a button disposed at the distal end of the housing, the button comprising a proximally-extending portion with an inward protrusion configured to slidably engage a distal portion of the sleeve.